The optical absorption and scattering properties of biological tissue depend on both the chemical and structural properties of the tissue and the wavelength of the interacting light. How these absorption and scattering properties of tissue change as a function of light can be particularly useful, as it is often unique to chemicals or structures in the tissue (the spectrum of the tissue). For example the absorption features of oxy- and deoxy-hemoglobin can be used to measure the oxygenation of blood and tissue, and the scatter changes caused by difference cellular sizes can be used to detect precancerous and cancerous tissue. The field of measuring these changes in optical properties, as a function of light, is known as spectroscopy and the device to measure the light at the various wavelengths is known as a spectrometer. Spectroscopy has found a wealth of current and potential applications in medicine.
Traditional spectrometers measure the spectrum of light from a single point of a sample. However, the spectrum from multiple spatial points can be combined to form a 3D spatial dataset (sometimes referred to as a hypercube), where the first two dimensions are spatial and the third is wavelength. In other words, each image pixel has an entire spectrum rather than just an intensity or RBG value. This is known as hyperspectral imaging and is a powerful technique as spatially resolved tissue chemical or microstructural properties can imaged, thus providing a more complete understanding of the tissue and may be a useful technique for tissue differentiation. According to a paper by Dicker et al [Differentiation of Normal Skin and Melanoma using High Resolution Hyperspectral Imaging], hyperspectral image analysis (or hyperspectral imaging) was applied to search for spectral differences between benign and malignant dermal tissue in routine hematoxylin eosin stained specimens (i.e., normal and abnormal skin, benign nevi and melanomas). The results revealed that all skin conditions in the initial data sets could be objectively differentiated providing that staining and section thickness was controlled.